Called when this window or a child window receives a keyboard event. The on-subwindow-char method of the receiver's top-level window is called first (see get-top-level-window); if the return value is #f, then the on-subwindow-char method is called for the next child in the path to the receiver, and so on. Finally, if the receiver's on-subwindow-char method returns #f, the event is passed on to the receiver's normal key-handling mechanism.
BEWARE: The default on-subwindow-char in frame% and on-subwindow-char in dialog% methods consume certain keyboard events (e.g., arrow keys, Enter) used for navigating within the window. Because the top-level window gets the first chance to handle the keyboard event, some events never reach the ``receiver'' child unless the default frame or dialog method is overridden.
The event argument is the event that was generated for the receiver window. Returns #f.